Characteristics

• General term encompassing a spectrum of conditions including chronic bronchitis and emphysema.

• Characterised by chronic resistance to expiratory airflow from infection, mucosal oedema, bronchospasm and bronchoconstriction, due to reduced lung elasticity.

• Causative factors include smoking, chronic asthma, alpha-1 antitrypsin deficiency and chronic infection.

Clinical features

• Exacerbations commonly precipitated by infection.

• Cough, wheeze and exertional dyspnoea.

• Tachypnoea, wheeze, lip pursing (a form of PEEP), use of accessory muscles.

• Cyanosis, plethora and signs of right heart failure suggest severe disease and cor pulmonale.

• Signs of hypercarbia include coarse tremor, bounding pulse, peripheral vasodilatation, drowsiness, confusion or an obtunded patient.

Radiological features

• CXR – only moderately sensitive (40–60%), but highly specific in appearance. Is an easily accessible method of assessing the extent and degree of structural parenchymal damage.

• Assessment for complications such as pneumonia, lobar collapse/atelectasis, pneumothorax or mimics of COPD.

• CXR features include hyper-expanded lungs with associated flattening of both hemi-diaphragms, ‘barrel-shaped chest’, lung bullae, coarse irregular lung markings (thickened dilated bronchi) and enlargement of the central pulmonary arteries in keeping with pulmonary arterial hypertension.

• REMEMBER to look for lung malignancy/nodules; a common association.

• CT – quantifies the extent, type and location of emphysema and bronchial wall thickening. It may also identify occult malignancy.

Differential diagnosis

• Lymphangioleiomyomatosis (LAM) and Langerhan's cell histiocytosis (LCH) can have a similar CXR and CT appearance. The clinical history and imaging together are diagnostic.

• Asthma ± superimposed infection.

• Extrinsic allergic alveolitis.

• Viral infections.

Management

• Supplemental oxygen tailored to keep pO2 > 7.5 kPa. Beware high concentrations of supplemental pO2, as patients fail to expel the CO2 and develop high pCO2 levels.

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